With the increasing environmental pollution, the environmental problems become more and more concerned by the society, more particularly, closely related to human health, the air environmental issues in the small environment is much more concerned. Ammonia is a colorless gas with highly irritating odor, which is lighter in density than air (the relative specific gravity is about 0.5), and its lowest sensible concentration to the human body is 5.3 ppm. When the ammonia contacts with the body's skin tissue, it will not only stimulate the role, but also will corrode the skin. Ammonia can denature proteins through absorbing water in the skin, so as to saponify the fat in the tissues, and to damage cell membrane structure. As ammonia has a high solubility, it will mainly result in stimulation and corrosion to the upper respiratory tract of animal or human body, to weaken the body's ability to resist disease. When its concentration is too high, it will induce cardiac arrest and respiratory arrest by the reflex of trigeminal nerve endings. However, the common ammonia gas sensor has high detection limit, poor selectivity, and complicated manufacture process. Therefore, a new ammonia sensor with low detection limit, high selectivity and simple preparation process is urgently needed.